The proposed NICHD Population Research Core Grant will operate within the Laboratories for Reproductive Biology to promote interdisciplinary research leading to better methods for the control of fertility and the treatment of reproductive disorders. Major emphasis has been placed on the male. A broad range of research centering on molecular mechanisms regulating male reproductive functions has been brought together in The Laboratories for Reproductive Biology. On- going work includes: Steroid and neuropeptide regulation of pituitary gonadotropin secretion and sexual behavior, cholesterol utilization in steroidogenesis, the identification and regulation of Sertoli cell factors that control spermatogenesis, regulation of gene expression in the sperm maturing regions of epididymis, post-testicular modifications of the sperm plasma membrane influencing fertilization, and growth factor requirements of early embryo growth and implantation. The shared Core Facilities included in the P-30 population center will provide histochemistry-microscopy, radioimmunoassay, tissue culture, recombinant DNA and administrative services. In addition to enhancing the productivity, quality and cost effectiveness of research, these cores will serve to nurture interdisciplinary collaboration among clinical and basic scientists within The Laboratories for Reproductive Biology. Eligibility for core use is requested for 34 funded research projects which will be active at the proposed start date of this application.